Hiroya Ohmori

Interatrial Electrical Connections: The Precise Location and Preferential Conduction

Background: The atria are assumed to be connected electrically to each other at the level of the Bachmanns bundle, coronary sinus (CS) musculature, and interatrial septum, and these connections may have an important role in the interatrial conduction and perpetuation of various types of atrial tachyarrhythmias. However, the number, location, and preferential connections of the interatrial conduction related to the site of activation have not been examined yet.

Intraoperative Electroanatomic Mapping

PURPOSE An electroanatomic mapping system using an electromagnetic navigation technology constructs a 3-dimensional structure of the heart with high geometric accuracy of the data that provides a precise localization of the substrates of arrhythmias. The system was tested for the feasibility and efficacy in intraoperative mapping. DESCRIPTION The strength of the magnetic field is measured by a location sensor with three different frequencies generated by a location pad placed beneath the operating table, and the spatial location of the sensor is determined. By roving the catheter on the heart while the local electrogram is recorded simultaneously, the 3-dimensional figure of the heart is reconstructed and an activation or voltage map is generated. EVALUATION The system was used in 19 patients with ventricular tachycardia or other arrhythmias. The focus or reentrant circuit of the tachycardia was precisely located and a map-guided procedure was successfully performed in all patients. Cardiopulmonary bypass allowed for the tachycardias to be mapped without any hemodynamic compromise. CONCLUSIONS Intraoperative mapping using the electroanatomic mapping system enables a precise localization of the tachycardia substrate.

A case of thoracoscopy-guided lead extraction with an excimer laser sheath

The patient was a 29‐year‐old male who had been diagnosed with transposition of the great arteries with an intact ventricular septum. At the age of 6 months, he underwent a Senning operation. At the age of 10 years, a dual‐chamber (DDD) pacemaker was implanted via the right subclavian vein for the treatment of sick sinus syndrome. At the age of 25, the generator was removed due to a lead fracture, and a new pacemaker was implanted via the left subclavian vein, leaving the previous lead in the right subclavian vein. Later, the patient developed pain in the right precordium, cramping of the major pectoral muscle, and non‐sustained ventricular tachycardia, suggesting physical stimulation of the left ventricle (functional right ventricle) by the residual leads. Therefore, lead extraction using an excimer laser sheath was planned. However, the leads adhered strongly to the vessels, and extraction was considered to involve a high risk of injury to the blood vessels, particularly the superior vena cava (SVC). We inserted a thoracoscope via the right precordial third intercostal space and observed the SVC via the thoracic cavity in order to immediately detect any complications. Using this approach, it was possible to extract the lead safely with an excimer laser sheath.

Double potential mapping: a novel technique for locating the site of incomplete ablation.

ObjectiveDouble potential mapping using bipolar electrodes that straddle the ablation line should identify the site of incomplete ablation as a conduction gap without constructing the activation maps. MethodsBipolar electrograms were recorded during pacing using 11 custom-made bipolar electrodes straddling the ablation line created by a bipolar radiofrequency ablation device on the lateral right atrium in seven canines. A linear ablation was made with an ablation device, of which one jaw was inserted into the atrium through a purse-string suture. A 3-mm-wide tape was placed on both jaws 10 mm from the tip of the ablation electrode to intentionally create an incomplete ablation lesion. The activation times at each dipole across the ablation line were defined as the times of the maximum positive and negative derivatives of the double potentials, and the site of conduction gap was determined as the site of the earliest activation across the linear ablation. The lateral right atrium was mapped simultaneously with 45 different bipolar electrodes to construct the activation maps and the earliest activation site across the ablation line was determined. ResultsThe double potential mapping located the conduction gap on a real-time basis without displaying any maps. There was no significant change in the accuracy between the different times after ablation and different pacing cycle lengths. ConclusionsDouble potential mapping locates the conduction gap on a real-time basis and would be useful in beating-heart epicardial ablation in off-pump setting.

Electrophysiological Mechanism of Lone Atrial Fibrillation

背景 現在,臨床で最もよく遭遇する不整脈に心房細動 がある.心房細動は,動悸などの自覚症状のほかに,血栓・ 塞栓症を引き起こす原因となるため,心房細動の発症機序 や治療法の確立は急務である.心房細動は,僧帽弁疾患な どに合併する心房細動と,明らかな基礎疾患を持たない孤 立性心房細動に分類される.弁膜症に合併する心房細動で は,左房に対する圧負荷あるいは容量負荷の結果として心 房筋のリモデリングを生じ,反復性巣状興奮の発生する器 質が発生すると考えられている.電気生理学的には肺静脈 の巣状興奮および右房のリエントリーが見られ,外科的治 療による高い治療効果が認められている.一方,全心房細 動の 10~30%を占めるといわれる孤立性心房細動では, その発症機序や心房興奮様式にいまだ不明な点が多く,治 療法も一定の見解は得られていない.よって孤立性心房細 動の心房興奮様式を解析することは,新たな治療法の確立 につながると考えられる. 図の解説 ヒトの心房より型をとったシリコンシート上 に 253 個の双極電極を配置したパッチ電極を作製し,心表 面に電極を接触させ心房細動中の心房電位を記録した.記 録された心房電位をマッピングシステムにて解析し,心房 興奮伝播図の 3次元表示を行った.マップでは,赤が早い 興奮を,青になるにしたがって遅い興奮を示した.上段に 体表心電図を,その下に心房各部位での心房電位を示し た.